General Broadband Pyranometers Frequently Asked Questions

1. General

1. Is it possible to have a single pyranometer that measures the combined UV-A and UV-B?

Yes, our model UVA-1 covers the entire UV-A and UV-B range of 280-400 nm ... but since only a tiny fraction of the integrated dose involves the UV-B range of 280-320 nm (compared with the total 280-400 nm range), what you are essentially measuring is UV-A.

2. When measuring with the UVB-1, from measured Volts out we change this values to UV erythematic via the correction table, but to evaluate the UV Index (UVI) the manual says to multiply by 25, the question is why 25? Other papers mentions a factor of 40?

Ideally you should use the tables and the solar zenith angle at the time of measurement. The origin of the multiply by 25 vs. divide by 40 is that some radiometers are calibrated in watts/m^2 while others are in calibrated in microwatts/cm^2. The difference between the two is a factor of 1000 (or 25 *40). This is a direct scale to the UV-Index, which was derived by WMO in 1994. There were UVB meetings at Diableretes, Switzerland in 1994 and 1996 to agree on this.